1. Field of the Invention
The present invention relates in general to very long lasting reserve power sources for powering devices, such as emergency medical devices and their means of activation and electrical storage and regulation, and more particularly to provide highly reliable reserve power sources for automated external defibrillators and the like.
2. Prior Art
An automated external defibrillator or AED is a portable electronic device that automatically diagnoses the potentially life threatening cardiac arrhythmias of ventricular fibrillation and ventricular fibrillation in a patient, and is able to treat them through defibrillation, the application of electrical therapy which stops the arrhythmia, allowing the heart to reestablish an effective rhythm. AEDs are designed to be simple to use for the layman, and the use of AEDs is taught in many first aid, first responder and basic life support (BLS) level CPR classes. Uncorrected, these cardiac conditions (ventricular tachycardia, ventricular fibrillation, asystole) rapidly lead to irreversible brain damage and death. After approximately three to five minutes, irreversible brain/tissue damage may begin to occur.
An AED is external because the operator applies the electrode pads to the bare chest of the victim, as opposed to internal defibrillators, which have electrodes surgically implanted inside the body of a patient. Automatic refers to the unit's ability to autonomously analyze the patient condition, and to assist this, the vast majority of units have spoken prompts, and some may also have visual displays to instruct the user.
The first commercially available AEDs were all of a monophasic type, which gave a high-energy shock, up to 360 to 400 Joules depending on the model. This caused increased cardiac injury and in some cases second and third-degree burns around the shock pad sites. Newer AEDs have tended to utilize biphasic algorithms which give two sequential lower-energy shocks of 120-200 joules, with each shock moving in an opposite polarity between the pads. This lower-energy waveform has proven more effective in clinical tests, as well as offering a reduced rate of complications and reduced recovery time.
Most manufacturers recommend checking the AED before every period of duty or on a regular basis for fixed units. Some units need to be switched on in order to perform a self check; other models have a self check system built in with a visible indicator.
Almost all portable AEDs, like those mounted on walls of offices, schools, airports, etc., are powered by regular primary or rechargeable batteries. The amount of charge available by such batteries and their performance, however, deteriorates over time. This is particularly a problem with AEDs provided for use in offices, schools and other public and private places, which may be used only once every several years. Such AEDs may very seldom be tested to ensure that their batteries can still be fully functional and the tests without the full load may not be reliable.
For an emergency medical device such as an AED, it is therefore highly desirable to provide power sources that are very long lasting without any degradation of their performance—preferably over the practical life of the device—and that can very reliably and rapidly provide adequate enough of electrical energy to power such medical devices.
In the disclosed embodiments of the medical devices such as AEDs, the power sources that are equipped with at least one reserve battery (such as the so-called liquid reserve or thermal battery with shelf life of up to 20 years or even longer) are utilized to ensure that the device can be powered reliably with the required amount of power in emergency situations.